If you knew anything about evolutionary biology, you'd know that polyandry, the practice of taking more than one husband, is an evolutionary aberration in human social structures because all human social structures would look exactly like lion prides or gorilla troops if nature took its proper misogynistic course. Men would sit around, ready to ward off hyenas, and women would do pretty much everything else. It's anthropology, you guys, plain and simple. Or it was, until two anthropologists surveyed the literature on polyandry and reminded everyone recently that polyandry among humans is way more common than conventional wisdom would have us believe.

The Atlantic's Alice Dreger identifies the roughly two dozen societies on the Tibetan plateau where polyandry exists as a legitimate form of mating and pair-bonding. Those plateau societies are a well-trod example, but, according to an article in the journal Human Nature by anthropologists Katherine Starkweather, a PhD candidate at the University of Missouri, and Raymond Hames, professor of anthropology at the University of Nebraska, there are way more instances of polyandry beyond the "classic polyandrous" Tibetan region. Starkweather's careful combing of anthropological accounts reveals 53 additional polyandrous societies living far afield from the Tibetan plateau:

Indeed, according to Starkweather and Hames, anthropologists have documented social systems for polyandrous unions "among foragers in a wide variety of environments ranging from the Arctic to the tropics, and to the desert." Recognizing that at least half these groups are hunter-gatherer societies, the authors conclude that, if those groups are similar to our ancestors — as we may reasonably suspect — then "it is probable that polyandry has a deep human history."

Rather than treating polyandry as a mystery to be explained away, Starkweather and Hames suggest polyandry constitutes a variation on the common, evolutionarily-adaptive phenomenon of pair-bonding — a variation that sometimes emerges in response to environmental conditions.

Polyandry, explains Dreger, is a solution to these environmental conditions, things like food scarcity or childcare insurance (it's important to have back-up husband on hand to provide socially-approved impregnation if something happens to first-string husband). The Bari people in Venezuela, for instance, have a system for recognizing two fathers of the same child, and this dual-fatherhood, according to anthropologists from Penn State, apparently gives children a better shot at surviving to age 15. The "two-dad" system is, according to Starkweather and Hames, "informal polyandry," because such societies may only recognize one of the men as a formal husband, but the important point is that systems like the one belonging to the Bari are all socially recognized.

Anthropologists came to think of polyandry as more of an aberration than it really is because, explains Dreger, ever since anthropologist George Murdock wrote in 1957 that almost no cultures exhibit polyandry "as the dominant and most preferred form of family life," anthropology has "accidentally been playing a scholarly version of the Telephone Game." Rather than understanding polyandry the way Murdock described it as "rarely culturally favored," anthropologists came to think that polyandry was rarely culturally permitted. That's a big difference, one that makes for all sorts of fun sexist implications:

In an email interview with me, Starkweather remarked, "I don't think that anyone, including Murdock, was operating from an explicitly sexist standpoint. However, I do think that the definitions of polyandry, and thus perceptions about its rarity, may have been due at least in part to the fact that an overwhelming percentage of anthropologists collecting data and shaping theory at the time were men." During Murdock's time, "there seemed to be a fairly pervasive belief that polyandry didn't make any sense from a male's perspective."

That explanation — that Western male anthropologists had a hard time "believing" in polyandry — makes sense. Humans appear prone, on average, to sexual jealousy, and so it would not be unreasonable for many of us — men and women alike — to project an assumption that sexual jealousy would make poly-unions untenable. Indeed, anthropologists have found that in both polyandry (one woman, multiple husbands) and polygyny (one husband, multiple wives), sexual jealousy often functions as a stressor in families around the world.

Ah, but Starkweather has helped adjust these anthropological misconceptions. Polyandry does occur, but often only when there are way more men milling around than there are fertile women, which has been, Hames says, the case among landowning societies way more often than polyandry has occured. How do landowning, non-egalitarian cultures deal with their dude surplus, in that case? It's pretty simple — they send them into the priesthood, tempt them into exploring the New World, or just ship them off to war. Problem solved! Landowning society can continue apace with its boring monogamy and polygyny.